An analysis of the effects of narcotics on the developing nervous system is important both practically in view of the widespread medical and nonmedical use of these drugs and theoretically because data on the effects of these compounds in the developing organism can provide valuable insight into how these drugs act at a mechanistic level. Our past efforts have been directed primarily toward setting up test systems in rats to document the use of pharmacologically active but nontoxic dose levels of narcotics and to examine the effects resulting in experimental framework upon which to base judgments about the importance and significance of any effects observed. The aim of the proposed work is to use this pharmacological framework to analyze the effects of narcotics at a mechanistic level. Specifically, this will involve studying the effects of selected narcotic agonists such as methadone and 1-alpha-acetylmethadol (LAAM) on the development of serotonergic, noradrenergic and dopaminergic systems in rat brain at selected stages of postnatal development.